High ionic thermoelectric performance in gel thermocells via the I−/IO3- redox couple

Effectively harvesting low-grade waste heat dispersed in the surrounding environment is critical for current energy recovery. Gel thermocells, which use ions as carriers to directly convert heat into electricity, have attracted increasing attention due to their high ionic thermopower and flexibility. However, the limited availability of redox couple poses a challenge to achieving high ionic thermoelectric (i-TE) performance. Herein, we propose a new redox couple, I − /IO 3 - , effectively utilized in the i-TE gel PAM/CMC-I - /IO 3 - -[HeMIM]Cl. By combining the thermogalvanic effect and the thermodiffusion effect, the i-TE performance is enhanced, demonstrating an n-type ionic thermopower of −11.1 mV K −1 and a normalized maximum output power density of 0.47 mW m −2  K −2 at 313 K. The mechanical properties of the i-TE gel exhibit 480% strain and strong adhesion to various materials. In addition, a gel device connecting twenty-five gel thermocells in series generates a high output voltage of 2.2 V, sufficient to drive a buzzer, highlighting the application potential of the i-TE gel with the I − /IO 3 - redox couple. This work broadens the range of redox couples applicable in i-TE systems, offering versatility for designing high-performance gels.